EM6821 datasheet(24/68 Pages) EMMICRO

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EM6821

www.emmicroelectronic.com

6.6.7 Reset and Sleep on Port SP

During circuit initialization, all option registers are reset by Power On Reset and therefore all pull-ups are off

and all pull-downs are on. During Sleep mode, Port SP inputs are cut-off , the circuit is in Reset State. However

the Reset State does not reset the option registers and pull-downs, if previously turned on, remain on even

during Sleep mode. After any reset the serial interface parameters are reset to : Slave mode, Start and Status

= 0, LSB first, negative edge shift , PSP[3:0] tristate.

Note : A write operation in the control registers or in the data registers while Start is high will change internal

values and may cause an error condition. The user must take care of the serial interface status before writing

internal registers. In order to read the correct values on the data registers, the shift operation must be halted

during the read accesses.

Figure 17 Shift Operation and IRQ Generation

SCLK = System Clock;

Active Edge = Neg. Edge;

Sense = MSB First

Clock Source

Shift Ck

Start

IRQ

Shift

SIN

OM[1]=1, OM[0]=0 : direct data out on pos. or neg. SCLK clock edge depending on bit POSnNeg

SOUT

OM[1]=0, OM[0]=1 : Re-Synchronized on positive SCLK clock edge data out

SOUT

10010011

01001100

Figure 18. Sample Basic Serial Port Connections

optional connection

External

EM 6621

SP[2]; SOUT

SP[3]; SCLKIn

SP[0]; SIN

SP[1]; Status

Serial Data In

Serial Clock Out

Serial Data Out

Ready

External

EM 6621

SP[2]; SOUT

SP[3]; SCLKOut

SP[0]; SIN

Ready

SP[1]: Status

Serial Data In

Serial Clock In

Serial Data Out

Status Output

Slave Mode

Master Mode

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